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Transcript
Kinds of Selection, evolution evidence
Natural Selection



Both Lamark and Darwin stated that species change
over time
Lamark hypothesized that environment causes the
changes in the organism
Darwin hypothesized that environment chooses
favourable variations, and that variation exists
because of the different genetic composition of the
population
Aritificial Selection

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Using the principles of natural selection to
domesticate wild organisms
Chosing desirable characteristics and selectively
breeding organisms
Ex: dog varieties for hunting, racing, herding etc.
Ex: plants selected for pest resitance, productivity
etc.
Accidental Selection

Humans create unintentional changes in the genetic
characteristics of organisms

Ex: DDT resistant insects

Ex: antibiotic resistant bacteria
Evidence that organisms evolve over
time

Direct Evidence: Fossils

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Provide evidence for how organisms have changed
Many fossils represent species that have gone
extinct
Others have undergone little change

Indirect Evidence: Looking for patterns such as
similarities and differences in species that are still
alive
a) Embryology
b) Anatomy
c) Vestigal structures
d) Physiological evidence
e) Biochemical evidence
Embryology


Study of organisms in the early stages of
developement
ex: what do the eggs look like? *see page 69
Anatomy

Homologous structures
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Similar structure, different function
Seal flippers and human arms have a different
function but similar origin
Analogous structures


Similar function, different origin of structures
Bat and insect wings perform the same function but
have different origins
Vestigal structures

Structures or organs which no longer have a function
(ex: human tailbone, male nipples)
Physiological evidence


Hormones which are the same between species
Hormones such as progesterone and estrogen for
human birth control pills come from horses
Biochemical Evidence

Similarities or differences between DNA

Our DNA has some similarities to primates
Patterns of evolution: Divergent
evolution

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When one species can evolve to give rise to many
different species
Ex: One ancestor species diverges into two new
species due to structural, behavioural or
physiological changes to adapt to various
environments
Homologous structures provide evidence for
divergence
Patterns of evolution: convergent
evolution


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When unrelated species develop similar
characteristics because of adaptations to a similar
environment and way of life
Ex: tasmanian wolf (marsupial from australia) and
Timber wolf (placental mammal from N.A.) Both
are predators that look similar
Analagous structures provide evidence for
convergent evolution (*see pg 78, fig 2.19)